In many applications it is desirable to have a variety of logic devices, memory devices, high frequency devices and devices capable of withstanding large transients (hereon referred to as power devices) all on a single substrate. One such type of power device is a double-diffused metal-oxide-semiconductor transistor (DMOS).
Heretofore typical high voltage processes do not support high performance bipolar transistors, which require a thin epitaxial layer and a buried layer. Long high temperature anneal steps required for typical high voltage processes are not compatible with buried layers under a thin epitaxial layer.
It is, therefore, an object of the invention to form high performance bipolar transistors in combination with high voltage DMOS transistors. It is a further object of the invention to perform a majority of the high-temperature process early in the process flow. Further objects and advantages of the invention will become apparent to those of ordinary skill in the art having reference to the following specification together with the drawings.